An airplane wing, with chord length of 1.5 m and span of 9 m, is designed to move through standard air at a speed of 7.5 m/s. a 1/10-scale model of this wing is to be tested in a water tunnel.
(a) what speed is necessary in the water tunnel to achieve dynamic similarity?
(b) what will be the ratio of forces measured in the model flow to those on the prototype wing? use tables a.8 and a.10.

Asolid cylinder is concentric with a straight pipe. the cylinder is 0.5 m long and has an outside diameter of 8 cm. the pipe has an inside diameter of 8.5 cm. the annulus between the cylinder ad the pipe contains stationary oil. the oil has a specific gravity of 0.92 and a kinematic viscosity of 5.57 x 10-4 m2/s. most nearly, what is the force needed to move the cylinder along the pipe at a constant velocity of 1 m/s?